Manufacture of resin-bound fiber structure



Sept; 1952 c. c. HERITAGE 2,610,138

MANUFACTURE OF RESIN-BOUND FIBER STRUCTURE Filed Nov. 27, 1945 far/kg Patented Sept. 9, 1952 MANUFACTURE OF RESIN-BOUND FIBE STRUCTURE Clark 0. Heritage, Cloquet; Minni', assignor to Wood Conversion Company, St. Paul, Minn, a corporation of Delaware l l i Application November. 27, 1945, Serial.No.631,11- 7 The present invention relates to the synthesis.

of mechanically rugged low density fibrous structuresexhibiting substantial strengths and. elasticities and particularly resistant to the action of liquid water, employing such hydrophilic materials asfcellulose, or lignocellulose ofanydesiredfl degree. of, lignification r delignification;

andaqueousdispersions of thermosetting'bindei's having water-insolubility when, thermoset It is old in generalto' form, fiber mats by mov ing, fibers through a spray of aqueous adhesive, feltingthe resulting adhesive-carrying fibers into a mati and drying the. adhesive and fiber withv onwithout compression, of] the wet, mat.

It has been ascertained that when an. aqueous.

solution of, certain and variousthermosetting resins are employed in an atomized. spray asthe adhesive for the fibers, a, useful blanket may or, may not beformed. For example, givena certain solution of phenolformaldehyde condensationproductffor forminga resin bindenand given a blanket-forming, procedure, a cellulosic matso formed is brittle and crumbles andlacks. utility; but a fewweekslater the, same materials and process may wellmake anexcellent ,useful strong and flexible blanket. A study-of tl1e.subjectihasl revealedthat the difference in said, mats. isa structural one, ,Thebrittleblanket has cellulosic fibersso,impregnated with the resin, that the resin is, set inside .the fibers, thus tending to embrittle them, and thus to leave very little resin forinterfacial contactsbetween fibers. The useful matj has its, resin-bearing fibers coated in whole or,in partwith a microscopicthin film of 'setresin, and hasfinterfacial layers of resin at contact points resulting from capillarydayers of" resinflsoluti on. provided by, the liquid film which is present on the fibers, when fibers wet with.the binder solution come into contact .in the, processing, andiparticularly when compressing before drying, I

' 'I 'h"ese studies have also revealed that the resin solution rmistbe such as preferentially to coat rather thanlto impregnate'the'fiber. No criteri-.

on except empirical test, has as yet been found todefine, the-resin solution, which, in addition,

may; be; variously defined in accordance with variations in the process or the fibers employed as wellas in other factors, However, it is known thatincrease in, viscosity characteristics of the resin; solution can eifect a non-impregnating property. Such viscosity can be increased, for example, by further advancing the resin, either in inanufacture, pr ,by heating or aging after.

manufacture,'byvarying the concentration of 2 Claims. (01. 154 -101) the. adhesive. solution, or by incorporating suit;

able thickening agents in the, solution.

It is, therefore; anobject offthe invention to."

produce resin-bound: cellulosic mat structures;

wherein t1' 16.fib81'$. acquire new. propertiea as fibers, by, reason of thin resin films carriedion and, bythem, andgwherein. such, fibers impart special property values-t0 the mat.

It is also an object to providea cellulosie fiber mat of whichthe fibers areso bound together. by

a water-resistant adhesive, and chemically blocked whereby the matretains. its structural entity in contact with water; and upon drying returns substantially to its initial quality.

It'is also anobiect toprovide'a mat ofwhich. the'fibersare at; least in part sosuriace-coated". with a thin 'filmof water resistantresin, that themat as a Whole is resistant to damageby water:

, It is anobject ofthe invention to produce a cellulosic fiber mat withawide-range of property values, by choice of fiber, choice" of resin, choice of resin, usage, choice of resin concentration in. adhesive solution, choice of density; and choice, of conditions regulatingthe ,interfelted' and. bonded relations of the'fibers, bothbefore, during and-after setting the resin.

The product of the invention may be made in various, ways, and in connection with the preferred way, the accompanying drawings, are

givenin explan'ation. In the drawings:

Fig. 1 represents a single fiber and two droplets liquid suspendedinair-and about to meet the (Fig. 2 ,represents the materialsof Fig; 11 after' the twodroplets have met-the fiber; and spread their solution content as liquid films over the Fig-J 3 represents a-second fiber'as having made contact with a wet film on the fiberof Fig; 2: 4 representsnumerousfibers in'a finished blanket with resin bonds atfiber junctions, and resin'coats elsewhere over portions of fibers.

Fig. 5 represents armat of'manyfibersin the relationship, shown in Fig. 4, but with. all the fiber surface coated with resin.

From, the foregoing general statements it will;

be clear that a given resin which penetrates and "impregnates the fibers, may be aged and.

" thus fthickenedf to a condition where it coats a fiber preferentially to penetrating it, It is to be understood, that there are intermediate and" borderline conditions with respect to' a given" processingof-fiber and'resin toform cured-resin.

=blanket, such that a change" of time from apply place.

ing resin solution to thermosetting the resin, will throw the borderline cases from one side to another. In other words, a resin solution may both coat a fiber and impregnate it, the impregnation being slow and drawing upon resin in the coat. The present invention aims to avoid complete impregnation with resulting brittleness of fiber and loss of coating resin, and to maintain a protective coat and surface-bonding quantity of resin. Thus, the time factor, resin qualities, and usage, are interrelated, and beyond precise definition.

Experience with the effect of water on the ability topenetrate the cell walls of wood when it is substantially unpolymerized. It is also described how the free polar groups combine'with polar groups of cellulose and lignin to cause loss of the hydrophilic properties arising in those groups. I v

However, where Stamm and Seborg desire entry of the resin-forming material into the cell wall, applicant desires to minimize or exclude such entry, and does so by using a mix moreadvanced than that of Stamm and Seborg. But in each case, the binder, being water-soluble, is not suificiently advanced to be free of reactive .polar groups. Thus, in applicants use where confinement to a coat is the objective, there can still be chemical bonding to the fiber by thev same mechanism described by-Stamm and Seborg. It is accordingly believed that the resin coato'r bond on the cellulos'ic fibers, is chemically bound to the fibers, thus giving the resin-bond its notable permanence against physical dislodgment, and thus imparting the high resistance to disintegration of the mat by liquid water.

Such a blanket'may be made by first providing a supply'of; individualized cellulosic' fibers for distribution as such.- Inthe case of wood and other lignocellulosic.vegetable matter providing in nature integrated bundles of such fibers, these bundles are broken up by physical or chemical action, or both. Thus, from vegetable matter,- chemical pulp, semi-chemical pulp or mechanical pulp, or the like, may be used. From wood, sulfite pulp, sulfite screenings, ground wood fiber, and many others, are available and have been used. I

The blanket may be made by coating the resin-forming aqueous solution on all or part of the fiber, -in' a very thin film, and then felting the fibers together while they are so wet, and setting the structure before absorption takes Where fibers come in contact at wetted surfaces thereof, they unite to a degree in wet form by capillary action. The wetted fibers so touching in a mat form, are then quickly dried by applied heat to react the resin supposedly with the fiber and also to set the resin which is located both on numerous fibers and at numerous contact regions. The wet mat before such drying may be variously manipulated and formed, but preferably it is merely compressed impregnate the fiber.

to a uniform thickness for drying. One or more compressions may be effected, multi-stage compression by rolls being preferred to single-stage compression.

The resin-forming solution is preferably aqueous. However, not all resin-forming solutions maybe used. Some such solutions penetrate the individual cellulose fibers, andsome do not. Some react properly to induce Water resistance, some do not. The solution must be such as readily to wet the surface of the fiber, and to coat it' superfically with a film of resin-forming material for a suitable time for permitting the desired physical manipulations which precede the heating and setting. The resin-forming solution must be such in character, for example, in molecular magnitude of its dispersed content, as preferentially to coat rather than to Those resin solutions which do penetrate the fiber, may carry resin to the interior, and if the ultimate resin is a brittle one, the finished fiber may be embrittledon setting the resin; and if an insufiicient quantity of such impregnating resin is ,em-.-' ployed so that coating beyond, an impfegna tion cannot be effected, there is a very poor bond and no useful blanket can result. ,Suitable synthetic resin-forming material which is water-soluble may be used. phenol-formaldehyde condensation products which are water-soluble, the resin-content can be insufiiciently polymerized in the binder solution, so that cellulose fibers are readily impregnated, and such a solution can be aged or its resin-content advanced so that it vwillpreferentially coat rather than impregnate the same fibers with a minimum of impregnation. Advancement should not be carried too far since both physical and chemical bonding are involved. Likewise, such solutions as willimpregnate by reason of the little-advanced resin content, may be rendered less impregnating by inclusion in the solution of a thickening agent, preferably one which is stable as such in the solution, as described hereinafter. v

The preferred manner of applying the binder solution to the fibersmerely to provide, film areas on the fibers for bonding with other fibers, is to atomize .the solution into a fog-like mass, and to disperse individualized fibers into this fog. The fog particles, having liquid which wets the fibers, thus hit and spread as collars or .en-

velopes around the fiber to the extent permitted by the'spreadability of the solution, its amount, and the surface area of the fiber. Some fibers may be entirely coated, and some partially coated, this being all a matter of chance involving also the size of droplets compared to a fiber. dles of fibers for such an operation, or clots'of individual fibers or bundles, are most undesired,- because a small amou'int of resin does little good, and the interior of the bundles or clots are unwetted; and because in the same circumstances a large amount of resin becomes housed in too'r'nany capillary pools, wastefully of resin for its ultimate function. Such two extreme conditions both lead to non-uniformity in a blanket resulting from deposition of such bindercoated clotted fibers.

The preferred method of depositing thebinder-coatedfibers is by the velocity of falling by gravity onto a like deposited layer. This is preferably done in a manner to provide a .uni-

formly thick mat, by employing a large gravity-.- depositing chamber into which individualized In the case r of Bun:

acraisa 57:, fi ers i er crablu dm; utzncrmissibly:moistaand msuitable; atomized ,hquid; binder; are=;;iniccted,, underuconditions'to. m xxand'dispcrs ,ghpinw the chamber and then; to. drop by ,gravity;-;onto a,.conveyor moving-ethrugh: the bottom of the chamber. l

mass of such gravityvdcpositeda bindere-wet individual fibers-isairagile layer andjhas no use-z ful tenacity or strength or; integration Each:

fiber; is merely piled .onothers. It-is ta, shiftablm 1 mass, very easily aupsetor compressed bymther slightest force,- to effect-both interfe'lting ofw-fibers and-=more fiben. contact junctions. Such? a F layer. as initially formed ataruniform, depth; ay" 5 inches, having ,a .ratioby dry-weight oiiabout. 7

toa25, parts of resin; solids .to -:100 parts'of icellulosefiber, may have a\ fiber-resin density of about Ailb}. per. cubicv foot. By control of l the process, its initially, depositedtdensity; may ,be greater or.

less. As formed, or. as slightly compressed after formation, the deposit becomespracticallyusefulwhendried and: bound, at: a density ofl aboutxfi lbhper; cubic foot. Insetting the-binder, asby drying, the,v fragile mass, becomes integrated and has practical utility. Its utility, increases at greater. densities, and for thermal insulation-p111;- poses, its utility' is limited at densities: overabout 5 lbs. percubicioot, For thermal insulation-pur poses=the practical..rangejof densitiesiis from about .5 toabout 5 lbs. vpercubic foot.- Fromthe o all-around stand-points of commercial production, handling, shipping, and installing. the preferred density range.iontheproducts. of theipresentinventionisirom li.to. .4 lbs. pencubic foot...

In compressin such. a gravity-deposited. layer wet with. unset, binder; the, fibers become :more felted, and more fibers contact other fib8IS,-giV-' ing' regions of potential. bonds, upon subsequent drying oi.;the.resinb'earing fibers. Thawet mat asdeposited; ther tore, acquires. more .strengthby; 40

interfelting ofthei. fibersfe fttcd bycoinpressihg. the: initial {deposit This is, important ,inQa Y, forming apparatus where the wehmatfiscouched. fromia forming wire-,toa. carrier wire] on, which it is dried. The mat'as' depositedfatfl a" density 7 (dry-weight) of'about .4 to1.5, 1b. percubiciootl 1 lb. densitywdry weight): and is readilytransfera able at about 1 lb. density Upon dryingyresin-bond's will occurnnly where resin-bearing i liquid" is presentat fiber" contacts: There may be contacts devoid of resin but there are-and must be comparatively" many contacts which are wet with resin. Density, resinusage, ahdfiber character, such-as' nbessizeanararm; all- :determine the relativeuunumben of contacts withresin bonds. I H

Resin concentration, resin prior to drying, time interval between coating and setting, densitysandfiber"characterall play their parts in the extent to which fi-ber portions in free spans of fibers the mat' are coated or are impregnated With resirr-bearing liquid? The' more 7 such coatingor impregnation, the'more-the final blanket: properties are affected and modified by resinicontent which is notbond. The dryresin on or in the free spans of fibers-"changestheproperty values mak-ing them stifier,*more-resistk usage, compressions nttocompre sionl w akerimt nsion. less-flexi le: and {H1018 waterrresistant: Because the; resint at-a the;- bond-is ,water sinsoluble; the :blanket resists; disintegrationwhen; subj cted tov water; 1 Such a: blanket can be-wplunged intowater; handled inthe s soaked :condition; and then dried WithQHtfIQSS D f 1 its integrity and with .littlechangein its property values; ,It hasa highi -wet strength when immersedin water.-. i

, In-,thed1'awings, the numeral; [0 is representae tive of a lignocellulosic fiber, such as a flatribbon form of sulfite-cooked;wood'fiber. Numerals II and l 2 represent droplets of atomized resin-forming; solution, such as will be hereinafter de scribed; for example, one which has approximate:T 1y;7% of-fresin-sol ids;therein of a phenol-formal dehydercondensation product stabilized in arkalinesolution, and so advanced or otherwise" processed that the solution does not eifectively impregnate the fiber'within the permissible time periodfrom coatingto thermosetting.

Fig: Zfrepresents the same fiber l0 after the droplets and I2, suspended in air with the fiber; have hit thefiber [0. The solution-readily wets-the fiber. Surface tension causesthe solution-to-spreadover the fiber as a thin film. In some cases, one, two,- or'even more dropletsmay contain enoughresinsolution completely to coat fiber 10, and this is the preferred condition. But for-the purposes of illustration, it is" shown that droplets and IZ-each coat an end of fiber 10, as shown at'regions l3 and-=14, leaving 'a dryun coated-area.

In-Fig: 3*fib'er l5 is represented: as a dry -fiber= which-*has "escaped" contact with a droplet of binder solution. 1 It is-illustratedashaving come' into contact with Wet'region 'I3-of fiber! [Land as. havin'g'robbed fiber It) of some of itsliquid coat l3; Thus; liquid from region I3in Fig. 2 may: supply capillary pools l6 at the junction of fibers lfl and 15, and also provide some Wetting film coats H and lB OILfiDBP I5, witha possibleg zdry" region IS on fiber I0 1 i Fig. trepresents a 'iragmentary portion of a very'loose mass ofisuch. coated fibers 20, showing: surface portions .21 coated, and other surface portions 22 uncoated, with fibers 5110113523, entirely coated; Upon compression it is obvious; that fiber contacts increase in number; with an increase in bond .by. the .binder thus located at,

fiber'contacts; r i

Eig. firepresents amass 2.4 of wet-coated fibers.v morerdense than the mat :illustrated-inFig; 1 4 as avresult of scompression to. a: uniform thickness; as :by compression, rolls, andv having, when, dry: av fiber-resin: density' of -1. toy5lbsz per cubicfoot.-. Theparallel rfaces are-indicated by 1 the, numerals 25Land'26s.

BINDER A A suitable resiniis made as followsz Y H By: Weight 1,000 parts a of phenoll (C'HsOI-D MLM-P'. 41 021 Lfiflo parts' offormalinir(37% by weight) solution of formaldehyde inswater; 60 parts 'of caustic soda dissolved in 98 partsiof water; are-reacted forBi'hours at 60 5 C: Then an: additional quantity 0f 60 parts of caustic soda dissolvedin'98 parts of water; is added; along with 1 parts of: water; The temperature is* raised to i80 "";C. and the heating continued until the .mass has aviscosity (at 25? C.) inthe rangerfromr 1,200 to :5,'OO0' centipoises. The material is tlieni cooled andis ready' for-use. Y

-'1"he:.f0regoing: corresponds to 1.85 moles'aJofl formaldehyde to Linoleof phenol. Thelzproducti'i,

;is an aqueous solution of the condensatiomprodari uctwhich is wen stabilized by the alkali contentagainst early gelling by normal advancement; prior to use. It may be stored-for several weeks at ordinary room temperature, and as freshly made or after such storage, the solids are still soluble in'the alkaline solvent. I It contains about 42% by weight of resin solids. When used to coat fibers, as by producing a fog as described, the reaction product is diluted with water to provides. solution having about 7% by weight of resin solids. I

1 BINDER B v By weight 20 parts of polyvinyl alcohol (saponification number of 12 to 90 where the material is the commercial hydrolyzed polyvinylacetate) is 1 added to 600 parts of formaldehyde as formalin in about 1,600 parts of 37% by weight solution inwater. 1 I v v When the polyvinyl alcohol is well dispersed, 1,000 parts of phenol (M. P. 41 C.) is melted and added to the said formalin. The mass is heated to 40 C. at which temperature 30 parts of caustic soda dissolved in 51 parts of water, is added. The mass is then heated to 80 C. during a heating period of 105 minutes, and the temperature of 804 C. is maintained until a specimen withdrawn and tested at 25 C. exhibits a viscosity of 1,200 to 1,300 centipoises. The holding time is about 4 hours. Then the mass is cooled to 60 C. at a rate of about 70 0. per hour, during which time the viscosity will increase by continued reaction by about 100 centipoises measured at 25 C. At-

60 C. or below, another 30 parts of caustic soda dissolved in 51 parts of water is added, thus increasing the viscosity measured at 25 C. by about 150 centipoises. When cooled to 45 C. (40 F.) the viscosity increases by about 50 centipoises measured at 25 C. The mass is stable for long periods, in some cases even for about one year,

without precipitation, or gelling, or appreciable change in viscosity. The final viscosity will be from 1,500 to 1,600 centipoises at 25 C.

As used in the present invention for producing a fog, it is suitable at a dilution to 7 resin solids.

In'the binders A and B, phenol and formaldehyde are used in the ratio of 1 mole to about 1.85 moles. The condensation is effected and polymerization is limited, to give an aqueous soluble product still reactive and polymerizable to insoluble form. Such binders tend to age thus to increase viscosity and finally to gel. To give adequate storage time permitting such advancement of the resin, and yet to give a desirable initial viscosity, the polyvinyl alcohol is employed in binder B. However, this is not essential, and may be omitted, of course where the resin solution is used while it remains as an ungelled solution. Thus, such solutions of binder diluted to about 7% for spraying to fog-particles, readily wet and coat cellulosic fibers without that degree of penetration which fully impregnates the fiber in a time on the order of about 1 to 11 minutes, which is the range of time interval which has been employed in actual practice between coating the fibers and entry of the compressed mat into a drier to dry and thermoset the resin on the fibers.

It is to be understood that shortening of the said time interval will in general permit using a more penetrating resin solution, While increasing the'time interval can make one which is suitable for the given range, unsuitable, by reason of the extended time permitting the resin solution, even though it be present initially as a coat, to strike into the fibers, disadvantageously to the product, and the economy...

' The drier is preferably steam-heated and such as to subject the wet mat to a drying temperature at or above the boiling point of water, the higher the better, up to a temperature of about 300 F.

above which, and particularly at 350 Fedesired properties are lessened by thermal degradation. The higher the temperature, the more rapid the rate of setting. In the examples hereinafter given, except as'otherwise noted, a large steamheated oven has been used into and out of which the mat moves, the operating temperature ranging upwardly from at or below 212 F. at the entry end to 230 F. just inwardly of the entry, and to 260 F. at the discharge end.

' Although the resin compositions above described provide brittle and not plasticized resin bodies, the mats boundwith such resin, in accorde ance with the present invention, are not brittle, and the bonds are not of such brittle character that they readily rupture. Because the fibers are not saturated, or even heavily impregnated with resin, the fiber exhibits some of its unimpregnated flexibility. Where a brittle resin is employed, a well impregnated fiber is embrittled. Thus, by choice of resin, and by timing, the flexibility of the product is controllable. It is pre ferred to minimize impregnation by use of suitably advanced, yet highly reactive, resin, which in solution as applied and as present while being dried and thermoset, remains as a coat with a minimum of impregnation.

However, using sufficient resin solution to leave a coat, impregnation may be permitted or even complete, where the fiber is not brittle after impregnation. The minimizing of impregnation in such case is for the purpose of preserving on the fiber a fluid liquid film to give a bonding quantityof resin upon drying as described.

In carrying out the process both thin and thick mats maybe produced in the same equipment. Thin matsmay be run faster, thus giving a shortened time interval. range of conditions a single binder supply is preferred, which operates at slowor fast speeds of themachine and on a wide variety of fibers. It has been found thatan aqueous liquid of phenol-formaldehyde condensation product, is thus useful, when meeting the following specifications:

Total solids content 39 to 41%.

Alkalinity 3.0 to 3.1% NaOH pH 9.9 to 10.0 Specific gravity 1.14 to 1.15

Viscosity at 25 C. 4000 to 7000 centipoises Refractive index 1.450 to 1.460

Water solubility miscible in all proportions Cure time at F.-. 10 seconds maximum BLANKET PROPERTIES The properties of the blanket may be made tovary over a wide range byselection of the fiber, selection of binder, variation of proportions of fiber to bindenand variation of processing conditions including compression of the blanket either before or after drying, or both. Properties ar e variously expressed as follows:

For use .over a wide rinc'xnnssmm DENSITY .=:AS'1:M stan ard a us to: d termi e h c "A specimen of afoot square of blanket is cemented with each broad faoetoplane surfaces,

which are pulled apart until medial rupture of thetblanket. Thes'tress atruptureuth'us becomes the bond; expressed in pounds per squareIoot.

TENSILE STRENGTH This isthe stress to rupture a itest specimen in crosssection. 1 Two opposite endsof afoot isquare specimen are clamped and 1 pulled. (apart to effect-rupture. The stress at rupture is ;ex

pressed as pounds per square foot of cross-sectional area.

' COMPRESSION Thisis the force to compress the blanket facewise *to one-third its uncompressed thickness. [Circles owns blanket having 6 inch diameter are cut and stacked to a pile not :over 3% inches high (for the apparatus employed). A plate on thepile; ismo vedyto compressthepile at,a"rate of 2:;inches ,per minute. The L compression 1 of the pile is arrested when the pile is one third of the initial pile 1 height, and then, at 80,.seconds from the initiation of compression the compression force :exerted .on .the. pile is read, and converted togpounds per; square foot facial-area.

. "RESILIENGE r51his isthe spring back,after-compression. ;In the compression test; at the said 80+secondsment onem e re nt t p e su e o i th :Pi ..1 .i1i leassdwsan yzth :.1 e. a we to aexpandw for; 55 seconds, after which it is substantiallygstable. The expanded volume is thenqmeasured. Resilience isv expressed; as the,per cent--recovery ofqthe whichyhaspreviously; been-wrapped about; a 5 6- inchtdiameter wooden mandrel. It isexpressed as zpounds pen square foot. Occasionally it .is

expressed as ;-:a percenta e ratio of tensile strength after rollingy to tensile strength before ollin t I v CONDUCTIVI'ITY '1-'Ihls is a'measure-of-themate ofheat transfer through a test specimen wherrmeasured the standard 12" ';x 12"? guatded-hotplates (as gspecified in tentative Methods of Test 1'Cl7'7-42T) It is expressed as B.t.u./hour/sq. ft./1F./inch of thickness of material under specified terminal temperatures.

ACIDITY OR ALKALINITY tilled.water for hour at 120.to 140 F. The

container is thenstoppered and'the zcontent cooled to room temperature. The solution is thentested for pH.

. COLLAPSE jThis is a measureofthe shrinkage in thick- 1 tress of a 1 foot square-testspecimen "soaked in i tvater for 15 minutes/drained for 15 minutes,

and dried out in an oven at 212 F. It is expressed-inper cent of the original thickness.

"RESISTANCE TO'COMMON MOLD PRODUC- ING ORGANISMS =Sterile specimens of'test material are placed in glass containers, each of which is then inoculated with one of four common mold-producing organisms. Penicillium Sp Aspergillus niger, 'Trichoderma Zignorium, and ,Chetomiwm plobosum. The containers are then tightly sealed 'atthe optimumjmoisture content to grow the particular (mold. "The following information is recorded "for comparative purposes: (1) The time in days to produce the firstvisual indication of mold, and (2). amount of mold growth after 30 days expressed as a visual judgment rating 0 to5;wherein"0=no moldgrowth and 5f=irnaximum mold growth."

,It is noted that the" phenokformaldehyde binderof the 'presentinvention gives protection against the above molds suclrthat the test shows no mold growth in 30'days.

WATER RESISTANCE ."ThiSl is expressed in. terms of tensile strength; which is :determinedafter: (l) soaking. for 15 minutes in water and draining for :15 minutes, and (2) soaking for 15 minutes in water, draining, and drying for 4.8 hours. Condition (1 is expressed-as wet tensile strength.

SVERSE STIFFNESS -;:!This is measured by the rateof deflection of a test tspeci'mensplaced .to overhang the edgeof a horizontal-plane surface with one foot of material projecting with self. support. It .isexpressed as inches deflection per foot of overhang at the. end of one minute.

-;-Table I PROPERTY VALUES 0E VARIOU 5.. BLANKE'IS j'Property (endunits) v6:293-214 1A B O D 4 D 1 E E I AQSTMjThiekness. it 1.14 ..ASTl\/L Density. 15 53 *Bond .45 Tensile'jStrength -.436 rTOomp'iession. q 138 Resiliencen 95. "Reliability.-. ls -;473 :TCollapsetsw)- "percent; 4 Thermal Oonducti y* (s ec .221 Ae'iditylor Alkalinity pH". 8.85 x' r'lra'nsverse Stiffness'KseeL. 1.34 -Wet;Iensile Strength... 338 ,After Soaking and Dryin' jiASTM-Thickfless 1.15. .ASTM Density... .1. 63 "Tensile Streng'th. 575

1 Different specimens.

11 Table I presents vertically various properties of different blankets, all bound with phenolic resin. The blankets are labelled horizontally at thetop of the table, and are as follows: S-293--214.

Table II 112 are the same as for Blanket D -above. The pronounced differences are in bond and collapse. The change from sulfitepulp to soda pulp improves the values of bond and of collapse.

BLANKET PROPERTY VALUES VITH VARYING USA GES AND CONCENTRATIONS OF RESIN-BINDER Wet Mat Dry Mat Sample Q I I I Rolla- V 7 Comp Resili- I S4586 Resin Fiber Resin Water E lgensity i' gf g gig fi nlgility 1bRes. Pence, 12 353? Usage Percent Percent Percent Inches s./cu t. lbsJsq. lbsJsq. ft it R 5553351 (See),

167. 7 49. 3. 15 47. 1. 05 1. 98 169 113 102 10 405 86 22 168 10 40. 25 4. D5 55. 5O 1. 14 2. 00 371 237 265 23 529 90 13 169 13 34. 33 4. 47 61. 20 1. 2O 2. 07 460 270 529 631 84 18 170. 15 31. 23 '4. 67 64. 10 1. 22 1. 97 539 315 487 51 574 89 16 171"". 17 28. 54 4. 86 66. 1.17 2. O0 636 330 537 4'8 714 9O 14 172. 19 26. 38 5. 02 68. 6O 1. 21 2. 09 641 1051 635 86 1! 173 24 22. U0 5 30 72. 1. 18 2. 13 721 363 655 81 657 86 10 PERCENT CONCENTRATION (FIXED RESIN USAGE AT 18 1.74- l 5 20. 41 3. 7 75. 8O 1. 17 2. [16 718 398 577 59 731 11 175 6 8 25. 67 4. 73 69. 60 1. 16 1. 92 582 331 658 51 510 86 11 176. 9 30. 78 5. 72 63. 5 1.18 1. 86 546 322 530 57 501 80 11 177. 11 34. G. 45 58. 6 1. 22 2. 00 487 297 534 44 458 85 12 This is a blanket made with a mixture of sulfite pulp and sulfite screenings. BinderB solution was used at 8.9% concentration of resin solids in quantity to provide a weight usage of 25.6 parts of resin per parts of fiber; This provides excellent insulation for refrigerator cars.

BLANKET A This is unbleached'sulfite fiber, using binder at 6.5% concentration of resin solids, at a weight usage of 16.2 parts of resin per 100 parts of fiber. The blanket provides excellent railroad car insulation.

BLANKET B The fiber consists of equal parts of sulfite pulp and sulfite screenings. By weight 18 parts of resin solids (at'7% concentration in water) are used per 100 parts of fiber. It makes excellent packing, as for delicate instruments.

BLANKET C Blanket D of sulfite jack pine was made from a moist mat wet-pressed to "V8 inches thickness, and after curing dry-rolled at a roll-height of' .75 inch. Blanket D is like Blanket D except that the wet-pressed thickness is 1.25 inches. For

All the foregoing show how the fiber character plays an important part in controlling or effect ing the final properties.

TableII shows the eiiects'of varying usage and concentration of binder B." The table is in two parts. In the top part, binder concentration is constant at 6 .8% and usage is varied as shown in the second column. The next three columns give the percent ratio by Weight as to fiber, binder solids, and water, in making the mat. In the lower part, the usage-is fixed at 18% and the concentration is shown in. the second column, which is the only column varying in the two parts of the table. i r

The fiber used is an unbleached 'sulfite pulp. The results indicatefor the series: (1) the dry and Wet tensile strength rise to a maximum at about 20% usage. (2) Bond rises rapidly, without reaching a maximum at 24% usage, and the high point "has not been reached at 24% usage.

(3) Collapse falls progressively with increased usage, and the low point has not been reached at 24% usage. (4) Compressive resistance rises toa peak at about 17% usage, then falls ofl at higher usages. (5) Resilience is not affected greatly by variation in binder usage. (6) Using more water and lower binder concentration, makes the blanket strongenbut water usageis a factor limited by the nature of the process.

I Low density blanket (5-474-75) .A mixture of dry sul'fite fibers, including 25% derived from sul fite screenings, is injected as a stream of individualized fibers into a settling chamber along with a fog-like spray of binder A at 7% concentration,

I i and in amount to provide 15 parts by weight of resin solids per 100 parts of fiber.

both blankets a formin Speed of 5.5 feet per min:-

' utes as a maximum. Binder A at 18% usage and 1.

7% concentration is used. The effects of fiber BLANKETS E AND E The mass as formed was heated and dried in an oven at 240 .F., without any compression to set the bond. It is specially characterized by lack of a smooth or skin-like surface, having, therefore an irregular surface texture, preferably obliterated in the pre- These show the relative effects of acid and j in the low-density blanket S47475. The initial alkali processes in pulping. Fiber for E is 100% aspen sulfite pulp. Fiber for E is 100% aspen soda pulp. v The resin and processing conditions ferred practice, by wet compression. The blanket has properties set forth in Table III below. Felt-like structure (8-474-76) is produced by processing the initial wet deposit which resulted deposit has a density of about .4 to .5 1b. (dry weight) per cu. it, It is wet-compressed, by rolls,

to about 3 lbs. density, at which the product can be readily transferred from a forming wire to a drier wire for entering a drying oven at a drying temperature as described. After drying, the mat was dry compressed to a density of 5.13 lbs. per

1 Value is greater than 5,100 but not indicated by particular test method.

From the foregoing illustrations it will be apparent that a wide variety of blankets may be made by use of the process described. The out standing property is resistance to water. This is of vital importance to use of such materials for insulation and for protective and cushioning padding. Use as insulation, in many conditions of poor design or uncontemplated circumstances, invites wetting by leakage or by vapor condensation. The ability to stand-up while wet and to dry out without loss of structure and insulating capacity is most important.

The present application is a continuation-inpart of a copending application executed by me, now abandoned and identified as Serial No. 467,040, filed November 26, 1942.

The invention in its numerous aspects is set forth in the accompanying claims.

I claim:

1. The method which comprises dispersing into a gaseous medium 100 parts by weight of dry substantially individualized cellulosic fibers derived from wood, and atomized fog-like particles of an aqueous alkali-stabilized solution containing on the order of about 7% by weight of dissolved phenol-formaldehyde resin-forming solids, in amount to supply from '7 to 25 parts of said resin solids by weight, said solution having the capacity readily to wet any of said fibers and spread over the surfaces of said fibers, thereby to provide a, film of said resin solution on a so-wetted fiber, causing said fibers and fog-like particles to mingle in said gaseous medium and to provide liquid film coatings on at least a major portion of said fibers and on at least a portion of the surface of a so-coated fiber, bringing the resulting mixture of fibers and carried liquid into felted-fiber-mat-forming contact whereby fiberto-fiber contacts are formed in the presence of liquid carried initially by at least one of any two contacting fibers, and drying the resulting mat at a thermosetting temperature for said resin before saturating impregnation of the fibers can occur, whereby to provide resin-bonds from fiber-tofiber and resin coats on at least some of the surfaces of the fibers.

2. The method which comprises dispersing into a gaseous medium parts by weight of substantially dry vegetable cellulosic fibers, and atomized fog-like particles of a dilute aqueous alkalistabilized solution in water containing dissolved phenol-formaldehyde resin-forming solids, in amount to supply from 7 to 25 parts of said resin solids by weight, said solution having the capacity readily to wet any of said fibers and spread over the surfaces of said fibers, thereby to provide a film of said resin solution on a so-wetted fiber, causing said fibers and fog-like particles to mingle in said gaseous medium and to provide liquid film coatings on at least a major portion of said fibers and on at least a portion of the surface of so-coated fiber, assembling the resulting mixture of fibers and carried liquid into a felted mat having a density in the range from about 0:5 to about 5 lbs. of fiber and resin per cu. ft. and suitable for direct thermosetting dryin to form a structure of density in said range, and drying the resulting mat at a thermosetting temperature for said resin before saturating impregnation of the fibers can occur, whereby to provide resin-bonds from fiber-to-fiber and resin coats on at least some of the surfaces of flexible fibers,

CLARK C. HERITAGE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,365,878 Weiss Jan. 18, 1921 1,966,458 Novak July 17, 1934 1,974,519 Steffens Sept. 25, 1934 2,070,330 Chase Feb. 9, 1937 2,136,827 Schur Nov. 15, 1938 2,288,072 Collins June 30, 1942 2,325,055 Heritage July 27, 1943 2,339,562 Eustis Jan. 18, 1944 2,363,480 Brownlee Nov. 18, 1944 

1. THE METHOD WHICH COMPRISES DISPERSING INTO A GASEOUS MEDIUM 100 PARTS BY WEIGHT OF DRY SUBSTANTIALLY INDIVIDUALIZED CELLULOSIC FIBERS DERIVED FROM WOOD, AND ATOMIZED FOG-LIKE PARTICLES OF AN AQUEOUS ALKALI-STABILIZED SOLUTION CONTAINING ON THE ORDER OF ABOUT 7% BY WEIGHT OF DISSOLVED PHENOL-FORMALDEHYDE RESIN-FORMING SOLIDS, IN AMOUNT TO SUPPLY FROM 7 TO 25 PARTS OF SAID RESIN SOLIDS BY WEIGHT, SAID SOLUTION HAVING THE CAPACITY READILTY TO WET ANY OF SAID FIBERS AND SPREAD OVER THE SURFACES OF SAID FIBERS, THEREBY TO PROVIDE A FILM OF SAID RESIN SOLUTION ON A SO-WETTED FIBER, CAUSING SAID FIBERS AND FOG-LIKE PARTICLES TO MINGLE IN SAID GASEOUS MEDIUM AND TO PROVIDE LIQUID FILM COATINGS ON AT LEAST A MOJOR PORTION OF SAID FIBERS AND ON AT LEAST A PORTION OF THE SURFACE OF A SO-COATED FIBER, BRINGING THE RESULTING MIXTURE OF FIBERS AND CARRIED LIQUID INTO FELTED-FIBER-MAT-FORMING CONTACT WHEREBY FIBERTO-FIBER CONTACTS ARE FORMED IN THE PRESENCE OF LIQUID CARRIED INITIALLY BY AT LEAST ONE OF ANY TWO CONTACTING FIBERS, AND DRYING THE RESULTING MAT AT A THERMOSETTING TEMPERATURE FOR SAID RESIN BEFORE SATURATING IMPREGNATION OF THE FIBERS CAN OCCUR, WHEREBY TO PROVIDE RESIN-BONDS FROM FIBER-TOFIBER AND RESIN COATS ON AT LEAST SOME OF THE SURFACES OF THE FIBERS. 